The invention relates to a needle thread changing device of a sewing machine that can automatically change a needle thread for another thread having different colors, kinds or the like.
A needle thread changing device of a sewing machine in which a thread currently using is knotted with a thread to be changed is disclosed in Examined Japanese Patent Publication No. Hei. 3-5834.
In the technology disclosed in the aforementioned publication, mechanisms for respectively holding a plurality of spools is arranged on a rotating table unit. Further, a predetermined actuator for clamping a thread end portion drawn from a spool is arranged for each holding mechanism. A single needle thread is selected from the plurality of spools and fed to the needle.
A currently used needle thread (changed thread) is changed for a new thread (changing thread) by cutting the currently used needle thread at a predetermined position on the head portion of the sewing machine, clamping the end portion of the currently used needle thread on the preceding thread side (the "preceding thread side" meaning a side of the cut changed thread to be knotted with a changing thread) with the predetermined actuator, and clamping the end portion of the changing thread on the spool side with the actuator arranged for the corresponding-holding mechanism. Then, the table unit is rotated to move the spool of the changing thread to a position confronting the head portion of the sewing machine, and the spool of the changing thread is moved toward the head portion of the sewing machine from the table unit together with the spool holding mechanism. Then, the end portion of the changing thread clamped by the actuator in the holding mechanism is set to the predetermined position (thread cutting position), and a knotting unit is driven to connect the end portion of the changing thread to the preceding thread.
However, the following problems have been addressed in the aforementioned conventional technology.
That is, the aforementioned technology requires that not only the table unit be rotated but also the spool of a changing thread be moved between the table unit and the head portion of the sewing machine together with the corresponding holding mechanism every time threads are changed. The aforementioned technology further requires a thread end portion clamping means for each spool.
For this reason, there exist problems that thread changing speed is slow and that sewing efficiency is low. In addition, since the mechanisms are complicated, the number of parts is increased, which in turn increases not only the structure of the device but also the cost of manufacture.
Therefore, an object of the invention is to provide a needle thread changing device of a sewing machine that can not only implement high sewing efficiency but also downsize the structure of the device and reduce the cost of manufacture by allowing threads to be changed without moving spools.
Another object of the invention is to provide a needle thread changing device of a sewing machine that can downsize the structure of the device and reduce the cost of manufacture by dispensing with a thread end portion clamping means per spool.
Still another object of the invention is to provide a needle thread changing device of a sewing machine that can facilitate the cleaning of the waste threads produced by the thread connecting operation.
According to a first aspect of the invention, there is provided a needle thread changing device of a sewing machine, comprising: a first thread end holding section for holding thread end portions of plurality threads respectively drawn from a plurality of spools; a thread cutting section for cutting a thread being currently used while selectively drawn from the first thread end holding section; a second thread end holding section for holding an end portion of the thread of a needle side cut by the thread cutting section; a thread selecting section for selecting a changing thread from the plurality of threads held by the first thread end holding section; a thread end portion moving section for moving an end portion of the thread selected by the thread selecting section to a predetermined knotting position; and a knotting section for connecting the end portion of the thread thus selected to the end portion of the thread currently used held by the second thread end holding section at the knotting position after the thread thus selected has been moved to the predetermined knotting position.
According to the needle thread changing device of a sewing machine of the first aspect, threads are no longer changed by moving the spool of a changing thread as in the conventional example. That is, a plurality of thread end portions respectively drawn from a plurality of spools are held by the first thread end portion holding section; a changing thread is selected from the threads held by the first thread end portion holding section; and the end portion of the selected thread is moved to a predetermined knotting position. Compared with the conventional example in which the spool itself is moved, the operation of moving the end portion of the thread drawn from each spool to a knotting position can be performed with a simpler means and within a shorter period of time.
Therefore, according to the needle thread changing device of a sewing machine, not only high sewing efficiency can be implemented but also the device structure can be downsized and the cost of manufacture can be reduced by allowing threads to be changed without moving spools.
According to a second aspect of the invention, there is provided the needle thread changing device of a sewing machine of the first aspect, wherein the first thread end holding section holds the thread end portions of the threads so as to hang down in a row.
According to the needle thread changing device of a sewing machine of the second aspect, the first thread end portion holding section holds the respective thread end portions drawn from the plurality of spools so as to hang down in a row. Therefore, there is no inconvenience in positioning the thread end portions for knotting even if there is no thread end portion clamping means per holding mechanism that holds a spool as in the conventional example.
Therefore, according to the needle thread changing device of a sewing machine of the second aspect, the device structure can be downsized and the cost of manufacture can be reduced by dispensing with a thread end portion clamping means per spool, in addition to the operation and advantages provided by the needle thread changing device of a sewing machine of the first aspect.
According to a third aspect of the invention, there is provided the needle thread changing device of a sewing machine described above, further comprising: a remaining thread discharging section for discharging thread portions remaining after the threads have been connected.
In the needle thread changing device of a sewing machine of the third aspect, the remaining thread discharging section that discharges thread portions remaining after the threads have been connected to a predetermined place is included. Therefore, the operation of cleaning the waste threads produced after the threads have been connected can be facilitated, in addition to the operation and advantages provided by the needle thread changing device of a sewing machine described above.
According to a fourth aspect of the invention, there is provided a thread changing device comprising; a sewing machine having a needle; a plurality of thread winding members, each having a thread; a first holding member for holding the respective threads in such a manner that the threads respectively paid off from the thread winding members are arranged along thread passages and are maintained so as to be substantially in parallel with one another; a selecting means for selecting a thread to be fed to the needle while moving the first holding means in a direction perpendicular to the thread passages; a thread cutting member being arranged closer to the needle than the selecting means along the thread passages and being movable to an operating position and to a return position, the operating position being a position at which the thread cutting member picks up a currently selected thread while crossing the thread passage of the currently selected thread, the return position being a position toward which the thread cutting member moves away from the operating position so that the thread cutting member draws near and cuts the picked up thread and holds an end portion of a cut thread portion extending to the needle; a pickup member being movable to an operating position and to a return position, the operating position being a position at which the pickup member picks up an end portion of a newly selected thread while crossing the passage of the newly selected thread, the return position being a position at which the pickup member draws near and holds the picked up end portion of the newly selected thread so that the pickup member holds the newly selected thread at a predetermined distance from the currently selected thread held by the thread cutting member with one of the threads up and the other down; and a knotting unit being parallelly movable to an operating position and to a standby position, the operating position being a position at which the knotting unit advances into the distance between the currently selected thread held by the thread cutting member and the newly selected thread held by the pickup member, the standby position being a position toward which the knotting unit moves away from the operating position, the knotting unit also knotting both threads at the operating position.
In the fourth aspect, advantages similar to those of the first aspect can be obtained in a thread changing device that connects a currently used thread to a changing thread by knotting threads in such a way as described in the invention.
According to a fifth aspect of the invention, there is provided the thread changing device of the fourth aspect, wherein the thread cutting member and the pickup member are located with one up and the other down, and the thread knotting unit is arranged so as to be distanced therefrom in a horizontal direction.
In the fifth aspect of the invention, the knotting unit can be moved linearly in the horizontal directions, which in turn allows advantages similar to those of the first aspect to be obtained.
According to a sixth aspect of the invention, there is provided the thread changing device of the fourth aspect, wherein the moving direction of the selecting means is parallel with the moving directions of the thread knotting unit.
In the sixth aspect, advantages similar to those of the fifth aspect can be obtained.
According to a seventh aspect of the invention, there is provided the thread changing device of the fifth aspect, wherein discharge members are arranged below the operating position of the thread cutting member and the operating position of the pickup member, the discharge members serving to scrap cut waste thread portions.
In the seventh aspect, advantages similar to those of the third aspect can be obtained.